The present invention is directed to a ferro fluid in combination with a piezo device for power generation. A piezo material is a material that can generate an electrical field in response to mechanical stress. Piezo materials include naturally occurring crystals, man made crystals such as gallium, orthophosphate (GaTO4) and langasite (La3Ga5SiO14), man made ceramics such as barium-titanate (BaTiO3), lead titanate (PvTrO3), lead zirconium-titanate (PZT) and polymers such as polyvinylidene fluoride (PvDF).
A ferro fluid is colloidal mixture of magnetic particles, less than ten nm in diameter, in a liquid carrier. The carrier contains a surfactant to prevent the magnetic particles from sticking together. The carrier can be water or organic fluid. A typical ferro fluid is about 5% magnetic solids, 10% surfactant and 85% carrier, by volume. One type of ferro fluid uses magnetite for the magnetic particles, oleic acid as the surfactant and kerosene as the carrier fluid to suspend the particles.
When no external magnetic field is present, the orientation of the magnetite or other magnetic particles is random. In other words, the magnetic ferro particles are not aligned with adjacent ferro particles when no external magnetic field is applied except possibly by happenstance. However, when an external magnetic field is applied, the ferro particles align with the magnetic field lines. When the magnetic field is removed, the particles return to random positioning. According to the present invention a ferro fluid with the above discussed properties is used in combination with a piezo material to stretch and induce stresses to the piezo material to thereby generate electric power.
US patents and patent publications disclosing magnetic fluids including ferro fluid include U.S. Pat. Nos. 6,899,338; 6,977,025; 7,063,802; 7,338,049 and US 2006/0215553.
It is heretofore been known to utilize a magnetostrictive material to induce stress in a piezo to produce power. Magnetostrictive materials are broadly defined as materials that under go a change in shape due to change in the magnetization state of the material and include common materials such as nickel, iron and cobolt in which the change in length is on the order of 10 parts per million when subjected to magnetization. Thus, the magnetostrictive material elongation growth is very limited. As a result, when magnetstrictive materials are used in combination with a piezo, the power is very limited.
Patents which show the use of RFID devices for use with tires include my U.S. Pat. No. 7,504,947. Other devices, including RFID devices, which may be incorporated on a surface of or within the structure of a tire for monitoring various functions relative to the tire include the following U.S. Pat. Nos. 5,562,787; 5,741,966; 6,062,072; 6,438,193; 6,856,245; 6,897,770; 7,009,576; 7,132,939; and 7,186,308. Patents which disclose devices utilizing piezo material with magnetostrictive material or other filler material include U.S. Pat. Nos. 6,809,516 and 7,069,642. The disclosures contained in these and the previously referenced patents are incorporated herein by reference.